This application claims the benefit of Korean Application No. 2002-39151 filed Jul. 6, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid electrophotographic image forming apparatus, and more particularly, to a liquid electrophotographic image forming apparatus in which a developer, to develop an image formed on a photosensitive body and an ink reservoir to supply ink to the developer are formed monolithically.
2. Description of the Related Art
In general, electrophotographic image forming apparatuses form an electrostatic latent image on a photosensitive medium, such as a photosensitive drum or photosensitive belt, develop the electrostatic latent image by a developing agent of a predetermined color, and transfer the developed image onto a sheet of paper, thereby forming a desired image.
Such electrophotographic image forming apparatuses are classified into a dry type and a wet type according to the type of the developing agent. Dry type image forming apparatuses use toner in a powder state, while liquid image forming apparatuses use a liquid developing agent, in which the toner is mixed with a volatile liquid carrier. The liquid image forming apparatuses have better printing quality than the dry type image forming apparatuses and reduce the risks of health problems caused by harmful toner dust.
FIG. 1 schematically shows the structure of a conventional liquid color image forming apparatus.
Referring to FIG. 1, a plurality of image forming units are arranged serially along a circulation route of a transfer belt 40, which moves on an endless track by a plurality of rollers 41, 42, and 44. Each of the image forming units transfers cyan (C), magenta (M), yellow (Y), and black (K) images, respectively, onto the transfer belt 40.
Each image forming unit includes a photosensitive drum 30, which transfers a toner image of a predetermined color onto the transfer belt 40; a charger 36, which charges the surface of the photosensitive drum 30 at a predetermined electric potential; a laser scanning unit (LSU) 38, which forms an electrostatic latent image by radiating light onto the charged surface of the photosensitive drum 30; a developing unit 10, which develops the electrostatic latent image into a predetermined toner image; and a cleaning blade 32, which removes a developing agent remaining on the photosensitive drum 30 after the developed toner image is transferred onto the transfer belt 40. Reference numeral 34 denotes an eraser that erases an electric potential on the photosensitive drum 30.
When the transfer belt 40 is supported and rotated by a driving roller 41, a second transfer backup roller 44 and a plurality of first transfer backup rollers 42 corresponding to the photosensitive drum 30, the image that is formed on the photosensitive drum 30 is transferred onto the transfer belt 40. A second transfer roller 43 is installed to rotate in a direction opposite to the rotation of the second transfer backup roller 44, and the transfer belt 40 is placed between the second transfer backup roller 44 and the second transfer roller 43. The second transfer roller 43 transfers the image on the transfer belt 40 onto a sheet of paper 60.
The paper 60 onto which the color image is transferred by the second transfer roller 43 is heated at a predetermined temperature and pressurized by a fusing unit 50 installed on a paper ejecting route, and the toner image is fixed on the paper 60.
FIG. 2 shows a detailed diagram of the image forming unit of FIG. 1 and illustrates a magenta developing unit 10-M among developing units having the same structure of FIG. 1.
Referring to FIG. 2, the developing unit 10 includes a developing portion 11, an ink reservoir 12 in which ink supplied to the developing portion 11 is stored, and a circulating portion 13 which circulates ink between the developing portion 11 and the ink reservoir 12.
The developing portion 11 includes a developing container 14 in which a developing agent (hereinafter, referred to as ink) is stored; a developing roller 15, part of which is dipped in the developing agent and installed to face the photosensitive drum 30; a depositing roller 16; a cleaning roller 17; and a metering roller 18.
Part of the developing roller 15 is dipped in the developing agent stored in the developing container 14. The depositing roller 16 is dipped in the developing agent stored in the developing container 14, and a predetermined voltage is applied to the depositing roller 16 being spaced apart from the developing roller 15 by a predetermined gap. The depositing roller 16 deposits the developing agent onto the surface of the developing roller 15 utilizing a difference in an electric potential between the depositing roller 16 and the developing roller 15 having the predetermined voltage.
The metering roller 18 is installed to be adjacent to the developing roller 15 and regulates the developing agent placed on the developing roller 15 to a predetermined thickness.
An ink feed hole 19 and an ink exhaust hole 20 are provided in the developing container 14. The circulating portion 13 includes an ink feed route 21 that connects the ink reservoir 12 to the ink feed hole 19 of the developing container 14, and an ink withdrawal route 22 that connects the ink reservoir 12 to the ink exhaust hole 20 of the developing container 14. A pump 23 is installed on the ink feed route 21.
Ink withdrawn from the ink reservoir 12 by the pump 23 is supplied to the developing container 14 via the ink feed route 21 connected to the ink feed hole 19. Since the developing agent in the developing container 14 is maintained at a uniform level, ink that exceeds this level is withdrawn to the ink reservoir 12 via the ink withdrawal route 22 connected to the ink exhaust hole 20.
According to the above-mentioned structure, ink withdrawn from the ink reservoir 12 passes through the ink feed route 21, the developing container 14, and the ink withdrawal route 22, back to the ink reservoir 12.
However, according to the structure of FIG. 2, an additional ink reservoir 12 is needed to supply ink to the developing portion 11, a hose is required to form an ink circulation route between the ink reservoir 12 and the developing container 14, and the pump 23 is used to supply ink, thereby increasing the volume of the image forming apparatus. In addition, the hose may be clogged by ink. Thus, when replacing the hose or ink reservoir 12 with another one, it is difficult to attach and detach a coupler (not shown) to and from the hose or ink reservoir 12, and accordingly, ink may leak out of the unit.
Accordingly, it is an aspect of the present invention to provide a liquid image forming apparatus in which a developing portion and an ink reservoir are formed monolithically and a unit to supply ink to the developing portion.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention are achieved by providing a liquid image forming apparatus comprising: a developing portion in which a developing roller to develop an electrostatic latent image formed on a photosensitive body in a predetermined color is installed and which is maintained at a uniform level so that the developing roller is dipped at a predetermined level; an ink reservoir in which ink supplied to the developing portion is stored; and an ink supplying unit that supplies ink stored in the ink reservoir to the developing portion. The developing portion and the ink reservoir are provided in one developing container. The ink supplying unit includes a barrier wall by which the developing container is divided into the developing portion and the ink reservoir and a lower part of which is opened, and an ink supplying roller which is installed to contact the lower part of the barrier wall and a bottom surface of the developing container and supplies ink in the ink reservoir to the developing portion.
The ink supplying roller is compressed by a lower end of the barrier wall, passes through the lower end of the barrier wall, expands, absorbs ink in the ink reservoir, meets the lower end of the barrier wall and is compressed when rotating, and ejects ink in the developing portion.
The apparatus further includes a protrusion which projects to correspond to the ink supplying roller in a direction of the barrier wall and is formed to compress an outer surface of the ink supplying roller on the bottom surface of the developing container contacting the ink supplying roller, and wherein the ink supplying roller passes through the protrusion, expands, absorbs ink in the ink reservoir, meets the protrusion and is compressed when rotating, and ejects ink in the developing portion.
In an aspect of the invention, an elastic porous material is formed on the outer surface of the ink supplying roller.
The apparatus further includes a photosensitive drum on which an electrostatic latent image developed by the developing roller is formed, an eraser which erases an electric potential on the photosensitive drum, and an exposing unit which forms an electrostatic latent image on the erased photosensitive drum. The above elements are provided in the developing container and form a single image forming unit.
The foregoing and/or other aspects of the present invention may also be achieved by providing a liquid image forming apparatus comprising: a developing portion in which a developing roller that develops an electrostatic latent image formed on a photosensitive body in a predetermined color is installed and which is maintained at a uniform level so that the developing roller is dipped at a predetermined level, an ink reservoir in which ink supplied to the developing portion is stored, and an ink supplying unit that supplies ink stored in the ink reservoir to the developing portion. In an aspect of the present invention, the developing portion and the ink reservoir are provided in one developing container. The ink supplying unit includes a barrier wall by which the developing container is divided into the developing portion and the ink reservoir and a lower part of which is opened, a cylindrical casing, upper and lower parts of which are fixed between the lower part of the barrier wall and a bottom surface of the developing container, having openings at both sides formed to face the developing portion and the ink reservoir, respectively, an axis eccentric in the cylindrical casing, and a plurality of impellers, one end of each impeller being fixed on the eccentric axis.
In another aspect of the invention, the eccentric axis is eccentric in the casing in a direction of the developing portion.
In yet another aspect of the invention, the impellers are formed of elastic rubber.